Moccasin Detention Dam Reservoir Report
Last Updated: December 25, 2025
Moccasin Detention Dam, located in Nashua, Montana, was completed in 1957 by the Bureau of Land Management for fire protection, stock, and small fish pond purposes.
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Summary
This gravity dam stands at a structural height of 22 feet and has a hydraulic height of 19 feet, with a length of 808 feet. It has a capacity to store up to 507 acre-feet of water, with a maximum storage of 420.35 acre-feet.
The dam is situated on Willow Creek, a tributary of the Milk River, in Valley County, Montana. With a low hazard potential and an unsatisfactory condition assessment, the dam is inspected every five years to ensure its stability and functionality. The spillway, classified as uncontrolled, has a width of 3 feet. Despite its moderate risk rating, the dam has not undergone any significant modifications since its completion.
Managed by the Bureau of Land Management, Moccasin Detention Dam serves as a vital water resource in the region, contributing to water conservation efforts and providing essential services for the local community. With its historical significance and continued importance in water management, the dam remains a key feature in the landscape of Montana's water infrastructure.
Year Completed |
1957 |
Dam Length |
808 |
River Or Stream |
WILLOW CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
58.08 |
Hydraulic Height |
19 |
Drainage Area |
7.9 |
Nid Storage |
507 |
Structural Height |
22 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
22 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Moccasin Detention Dam